/6 head bolt + ring and bearing suggestions please.

With soap and hot water and dedication you will be able to clean the block.
Get some long handle bottle brushes for cleaning the oil lines.
If you can get a power washer that will make you job easier.
Purple Power is a good greaser, oven cleaner may also be your friend.
If re using the rocker arms, give those a through cleaning, carb cleaner is good for blowing through the oil passages.
The rocker shaft should have the cup plugs pulled and scrubbed internally and the oil pump pressure relief valve should be serviced.